With the increasing proliferation of wireless technology, such as Wi-Fi, Bluetooth, and mobile or wireless Internet of things (IoT) devices, more devices or systems incorporate radio frequency (RF) circuitry, such as receivers and/or transmitters. A variety of types and circuitry for transmitters and receivers are used. Transmitters send or transmit information via a medium, such as air, using RF signals. Receivers at another point or location receive the RF signals from the medium, and retrieve the information.
The RF circuitry typically uses antennas to receive (in the case of receivers) or transmit (in the case of transmitters) RF signals. To increase performance, such as throughput, bandwidth, speed, etc., the RF circuitry may use multiple antennas. The multiple antennas may be used in a variety of schemes, such as beam-forming, antenna diversity, multiple-input and multiple-output (MIMO), etc. For example, some wireless communication standards, such as IEEE 802.11n, IEEE 802.11ac, HSPA+, WiMAX, and Long Term Evolution (LTE) use MIMO techniques. Modulation techniques are used to address problems in a MIMO setting, such as multi-path communication channels.
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